MICROBIOLOGICAL DETERIORATION AND EFFECTS OF ENVIRONMENT ON STORABILITY OF SHELLED CORN STORED AT SIMULATED MIDWEST AND SOUTHEAST U.S. CONDITIONS (PENICILLIUM)
Abstract
Shelled corn of high quality was stored at 14.0, 15.5, and 18.0% MC for 7.0 or 7.5 mos at Indianapolis temperatures (IT) starting Oct. 15. After 2.5, 3.5, 5.5, and 7.0 or 7.5 mos, aliquots were transferred to 84% RH or kept at their original moisture at 26 C for 21 days. The latter conditions represented transport to southeastern United States. Mold spoilage was determined by examining kernels for visible molds, blue eye, kernel invasion, and fungal propagules. The corn of 14.0 and 15.5% MC was "safely stored" for 7.5 mos at IT, but only 6.5 mos for 18.0% MC corn. The length of previous storage and moisture influenced storability of the corn when exposed to 84% RH at 26 C. Corn stored for 7.5 mos, even when not invaded by fungi, were more predisposed to development of storage molds than corn stored for 5.5 mos or less. To predict mold spoilage of corn in shipment to southeastern United States, storage history and conditions of transport should be considered. Penicillium (122 isolates) from commercial samples and corn stored at experimental conditions were identified by Raper and Thom's monograph supplemented by Pitt's and Frisvad's physiological tests. Temperature requirements for colony growth separated species into field and storage Penicillia and aided identification. Field Penicillia were: P. oxalicum (7.4%) and P. funiculosum (6.6%). Storage Penicillia were: P. cyclopium (23%), P. viridicatum (23%), P. brevi-compactum (14%), P. frequentans (12.2%), P. urticae (6.5%), and P. palitans (3.3%). P. variable (4%) was intermediate in temperature requirements. Field Penicillia grew fastest at 30 C (maximum 36-37 C), storage Penicillia at 24 C (minimum 4-5 C). Penicillum spp. were screened for 6 mycotoxins: citrinin, cyclopiazonic acid, ochratoxin, patulin, penicillic acid, and xanthomegnin. The no. of positive/total tested were: ('0)/20 citrinin, ('0)/496 cyclopiazonic acid, ('0)/496 ochratoxin, ('0)/158 patulin, ('3)/50 penicillic acid, and ('11)/87 xanthomegnin. ('3)/20 P. cyclopium isolates and ('11)/29 P. viridicatum isolates were positive for penicillic acid and xanthomegnin, respectively.
Degree
Ph.D.
Subject Area
Plant pathology
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